2.1.3 Nucleotides And Nucleic Acids

Question 1

Nucleotides

Answer 1

Monomers, CHONP
Make DNA and RNA.

• Pentose sugar
• Nitrogenous base
• Phosphate group

Question 2

Pentose Sugar

Answer 2

• Deoxyribose
• Ribose

Question 3

Nitrogenous Bases

Answer 3

Adenine, Thymine (or Uracil), Cytosine, Guanine

Adenine - Thymine/Uracil
(2 H bonds)

Cytosine - Guanine
(3 H bonds)

Question 4

Purine

Answer 4

Two carbon nitrogen rings - bigger

Adenine, Guanine

Question 5

Pyrimidine

Answer 5

One carbon nitrogen ring - smaller

Cytosine, Thymine/Uracil

Question 6

DNA

Answer 6

• A, T, C, G
• Two polypeptide chains
  -Deoxyribose

Question 7

RNA

Answer 7

• A, U, C, G
• One polypeptide chain
• Ribose§

Question 8

ATP and ADP

Answer 8

Adenosine triphosphate.
Adenosine diphosphate.
Add a phosphate to become ATP, take one to become ADP.

Question 9

Formation of Polynucleotides

Answer 9

• Phosphodiester bond between a phosphate on one nucleotide and sugar of another nucleotide.
• Condensation and hydrolysis

Question 10

Double Helix

Answer 10

There are H bonds between bases. Each base joins with one partner, complementary base pairing.
Two anti parallel strands.

Question 11

Precipitation Reaction - Purifying DNA

Answer 11

• Break up cells using pestle and mortar
• Solution of detergent (breaks down membranes), salt (causes clumping of DNA), distilled water
• Add broken up cells to a beaker containing solution
• 60 °C water bath for 15 mins (denature enzymes that break down DNA)
• Ice bath to cool and filter
• Add protease (break down proteins like histones and RNAase breaks down RNA)
• Ethanol to form a layer
• Observe precipitate

Question 12

DNA Replication

Answer 12

• DNA helicase breaks H bonds and unzips strands so the bases are exposed
• Bases line up with complementary free nucleotides and are joined
• DNA polymerase catalyses formation of phosphodiester bonds and sugar phosphate backbone
• H bonds form and form a new double helix
• 1 original, 1 new - semi conservative replication

Question 13

Genes

Answer 13

Sequence of DNA nucleotides that code for a polypeptide. The order determines the order of amino acids. A triplet/codon codes for an amino acid.

Question 14

Why DNA is transcribed into RNA

Answer 14

DNA is too large to move out of the nucleus so a section is copied.

Question 15

mRNA

Answer 15

• Made in nucleus
• Carries genetic code from nucleus to cytoplasm onto a ribosome

Question 16

tRNA

Answer 16

• Cytoplasm
• Amino acid binding site with anticodon
• Carries the amino acids to the ribosomes during translation

Question 17

rRNA

Answer 17

• Forms subunits of ribosomes along with protein

Question 18

Genetic Code

Answer 18

The sequence of base triplets in DNA or MRNA.

Question 19

Non Overlapping

Answer 19

Each base is read in sequence, base triplets don’t share bases.

Question 20

Degenerate

Answer 20

More combinations of triplets than amino acids, some are coded for by more than one base triplet. 20 amino acids, 64 base triplets

Question 21

Universal

Answer 21

Same base triplets code for the same amino acids in all living things.

Question 22

Transcription

Answer 22

• RNA polymerase attaches to double helix and breaks H bonds to unwind, one strand used as a template/anti sense strand
• RNA polymerase lines up free RNA nucleotides and complementary base pairing occurs
• RNA polymerase assembles strand
• DNA recoils
• Detaches at STP
• Nucleus to Cytoplasm

Question 23

Translation

Answer 23

• mRNA attaches to ribosome and tRNA brings amino acids
• A tRNA with a complementary anticodons attach to the start codon
• Second tRNA attaches to second codon and both produce amino acids
• Peptide bond formation
• Carries on until STP codon